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Jun 29, 2018
06/18

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Elizabeth Hou; Earl Lawrence; Alfred O. Hero

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The ensemble Kalman filter (EnKF) is a data assimilation technique that uses an ensemble of models, updated with data, to track the time evolution of a non-linear system. It does so by using an empirical approximation to the well-known Kalman filter. Unfortunately, its performance suffers when the ensemble size is smaller than the state space, as is often the case for computationally burdensome models. This scenario means that the empirical estimate of the state covariance is not full rank and...

Topics: Physics, Data Analysis, Statistics and Probability, Applications, Atmospheric and Oceanic Physics,...

Source: http://arxiv.org/abs/1610.00195

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Jun 29, 2018
06/18

by
Jun Meng; Jingfang Fan; Yosef Ashkenazy; Shlomo Havlin

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Complex networks have been used intensively to investigate the flow and dynamics of many natural systems including the climate system. Here, we develop a percolation based measure, the order parameter, to study and quantify climate networks. We find that abrupt transitions of the order parameter usually occur $\sim$1 year before El Ni\~{n}o ~ events, suggesting that they can be used as early warning precursors of El Ni\~{n}o. Using this method we analyze several reanalysis datasets and show the...

Topics: Geophysics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1611.06056

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Jun 29, 2018
06/18

by
Victor Rodriguez-Mendez; Victor M. Eguiluz; Emilio Hernandez-Garcia; Jose J. Ramasco

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Abrupt transitions are ubiquitous in the dynamics of complex systems. Finding precursors, i.e. early indicators of their arrival, is fundamental in many areas of science ranging from electrical engineering to climate. However, obtaining warnings of an approaching transition well in advance remains an elusive task. Here we show that a functional network, constructed from spatial correlations of the system's time series, experiences a percolation transition way before the actual system reaches a...

Topics: Data Analysis, Statistics and Probability, Statistical Mechanics, Condensed Matter, Atmospheric and...

Source: http://arxiv.org/abs/1601.01978

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Jun 29, 2018
06/18

by
B. K. Sahoo; Madhulita Das

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The effect of plasma environment on the atomic energy levels of He-like and Li-like Mg and Fe ions have been studied using Debye model. The equation-of-motion coupled-cluster (EOMCC) and Fock-space coupled-cluster (FSCC) formalisms in the relativistic frame work have been adopted to describe the atomic states and the energy levels of the above plasma embedded ions. Salient features of these methods have been described to account the two electron screening effects through the Debye potentials....

Topics: Atmospheric and Oceanic Physics, Atomic Physics, Solar and Stellar Astrophysics, Physics,...

Source: http://arxiv.org/abs/1608.07919

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Jun 29, 2018
06/18

by
Richard S. J. Tol

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The Fisher Ideal index, developed to measure price inflation, is applied to define a population-weighted temperature trend. This method has the advantages that the trend is representative for the population distribution throughout the sample but without conflating the trend in the population distribution and the trend in the temperature. I show that the trend in the global area-weighted average surface air temperature is different in key details from the population-weighted trend. I extend the...

Topics: Physics, Quantitative Finance, Atmospheric and Oceanic Physics, Economics

Source: http://arxiv.org/abs/1612.09123

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Jun 29, 2018
06/18

by
Cecilia F. Mondaini; Edriss S. Titi

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We apply the Postprocessing Galerkin method to a recently introduced continuous data assimilation (downscaling) algorithm for obtaining a numerical approximation of the solution of the two-dimensional Navier-Stokes equations corresponding to given measurements from a coarse spatial mesh. Under suitable conditions on the relaxation (nudging) parameter, the resolution of the coarse spatial mesh and the resolution of the numerical scheme, we obtain uniform in time estimates for the error between...

Topics: Atmospheric and Oceanic Physics, Numerical Analysis, Analysis of PDEs, Physics, Mathematics,...

Source: http://arxiv.org/abs/1612.06998

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Jun 29, 2018
06/18

by
V. P. Ruban

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The numerical simulation of the nonlinear dynamics of random sea waves at moderately small Benjamin-Feir indices and its comparison with the linear dynamics (at the coincidence of spatial Fourier harmonics near a spectral peak at a certain time $t_p$) indicate that the appearance of a rogue wave can be predicted in advance. If the linear approximation shows the presence of a sufficiently extensive and/or high group of waves in the near future after $t_p$, an anomalous wave is almost necessarily...

Topics: Fluid Dynamics, Physics, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1609.00500

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Jun 29, 2018
06/18

by
Salvatore Rampone; Alessio Valente

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In this work two soft computing methods, Artificial Neural Networks and Genetic Programming, are proposed in order to forecast the mean temperature that will occur in future seasons. The area in which the soft computing techniques were applied is that of the surroundings of the town of Benevento, in the south of Italy, having geographic coordinates (lat. 41{\deg}07'50"N; long.14{\deg}47'13"E). This area is not affected by maritime influences as well as by winds coming from the west....

Topics: Physics, Neural and Evolutionary Computing, Computing Research Repository, Atmospheric and Oceanic...

Source: http://arxiv.org/abs/1611.04767

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Jun 29, 2018
06/18

by
Emma J. Barton; C. Hill; Sergei N. Yurchenko; Jonathan Tennyson; Anna S. Dudaryonok; Nina N. Lavrentieva

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Many atmospheres (cool stars, brown dwarfs, giant planets, extrasolar planets) are predominately composed of molecular hydrogen and helium. H$_2{}^{16}$O is one of the best measured molecules in extrasolar planetary atmospheres to date and a major compound in the atmospheres of brown-dwarfs and oxygen-rich cool stars, yet the scope of experimental and theoretical studies on the pressure broadening of water vapour lines by collision with hydrogen and helium remains limited. Theoretical H$_2$-...

Topics: Earth and Planetary Astrophysics, Astrophysics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1610.09008